This invention relates to a ball for ballgames and a manufacturing process therefor. The ball has a reasonable hardness, high restorability, high durability, makes a clear sound when hit by a bat and is easy to manufacture.
A conventional ball for ballgames, especially for baseball, is generally comprised of a core body made of hard synthetic resin, the circumference of which is covered by a semihard cover body, on which is provided a thin layer made of relatively soft material such as thread, the circumference of which is covered by an epidermal body.
However, such a conventional ball has disadvantages in that the weight of the core body is difficult to control and a clear sound cannot be made unless the core of the ball is hit in the right spot by a fairly strong force. To overcome these disadvantages, a ball has been proposed which is comprised of a molding of hard synthetic resin with cork pieces dispersed therein and on which is wound a relatively soft thin layer such as thread, the circumference of which is covered by an epidermal body.
The ball with the cork pieces has merit since weight control can be achieved easily by the adjustment of the volume of the cork pieces and a clear sound can be made because most of the core consists of hard synthetic resin. On the other hand, the ball has the disadvantage that it has poor restorability due to the predominence of hard synthetic resin.
A ball, at the moment it is hit by a bat, is deformed to an oval shape, of which the minor axis is half the normal diameter. If the restorability is insufficient, the ball is not restored to the original condition. When the warped ball is continued in use, smooth play is prevented by such an irregular shape.
In order to remove such a disadvantage, the present inventor previously proposed a ball suitable for baseball which is molded from hard synthetic resin, a light material such as cork and soft synthetic resin, the weight of which can be easily controlled, which can produce clear sounds when hit by a bat and which possesses sufficient restorability (Japanese Utility Model Lying Open No. 60-21108). Although the functions of this ball, such as flying distance and restorability, are quite satisfactory, the following disadvantages have been noted:
(1) The cork or the like is difficult to disperse uniformily in the synthetic resins because of poor affinity.
(2) A binding agent is required in order to adhere the cork or the like to the synthetic resins for the same reason.
(3) Cracks are liable to be produced at the interface of the cork and the synthetic resins because the hardnesses therebetween differ from each other.
(4) The weight of the ball is liable to be increased when water permeates the ball since cork is hygroscopic.